The present invention relates to a new and improved construction of a hydro-electric turbo-machine.
Generally speaking, the hydro-electric turbo-machine of the present development is of the type containing a rotor revolving within a stationary housing or casing and a substantially ring-shaped seal or sealing arrangement for sealing the water flowing through the turbo-machine between corresponding parts of the rotor and the housing. One of the parts constitutes a rigid counter part having a sealing surface against which there is pressed at least one sealing body formed of a resilient or compliant material and mounted in the other part.
With such type of hydro-electric turbo-machines, for instance water turbines, storage pumps, pump turbines or the like, possessing a large diameter of the runner or the hub assembly, for instance in the meter range, it is necessary to seal the water which is pressurized. Sealing of such pressurized water is accomplished, for instance, at the circumference of the runner, in order to prevent penetration of such pressurized water into an electric generator arranged, for example at the outer rim of the runner, or into the hub assembly, the diameter of which likewise can be in the meter-range, in order to prevent such pressurized water from reaching the bearings of the runner shaft. These bearings are located, for instance, at the central region or so-called bulbous portion of the housing or casing.
Seals for small diameters, for instance in the centimeter or deci-centimeter range, are already known in multifarious constructions. For instance, they are known to the art as shaft seals or retaining rings. As a general rule, they adequately satisfy the imposed requirements as to sealing tightness, good lubrication properties and sufficient longevity for those conditions which are encountered at these regions.
However, these seals which are entirely satisfactory for use when working with small diameters are no longer adequate for sealing revolving parts or components of large diameter and for complying with the thus prevailing requirements. For instance, for tube turbines there arise relative velocities of the revolving components or parts in a range considerably above 10 m/s, for instance in the order of magnitude of 50 m/s, which produce appreciable frictional forces.
In such instances, the wear of the sealing body therefore is appreciable and the service life or longevity of the seals is low. The deformations arising when working with large diamaters lie in part in the order of the millimeter range, so that considerably greater tolerances must be compensated than for the known seals used with smaller diameters. The use of the prior art seals with turbo-machines having large diameters therefore was heretofore unsatisfactory.
It has already been proposed to solve these problems in various ways. For instance, in U.S. Pat. No. 3,606,568, granted Sept. 20, 1971, there is described a water turbine whose seal consists of a double-bead ring. Both of these beads are hydraulically pressed against a sealing surface. While there is possible a certain tolerance compensation, nonetheless the frictional forces are still appreciable and the rapid wear of the sealing beads results in too low service life and a premature leakiness or untightness of the seal arrangement.
In German Pat. No. 1,151,155, published July 4, 1963, there is disclosed a ring-shaped seal possessing a lip seal, the lip member of which is pressed by the pressure of the medium which is to be sealed against a sealing surface. Also such type of seal construction experiences much too great wear and displays insufficient service life.
In the U.S. Pat. No. 3,346,265, granted Oct. 10, 1967 there is disclosed a double-lip seal arrangement for sealing oil in large-diameter machines. Also in this case there is required frequent exchange of the sealing arrangement because of wear and the like.
Also in U.S. Pat. No. 4,191,064, granted Apr. 15, 1980 there is disclosed a spring-reinforced lip seal having a diameter greater than one meter, but such seal arrangement equally does not possess an improved running characteristics.